Article Figures & Data
Figures
- Fig 1.
Sample whole-head 1H-MR spectroscopy spectra from each of the MR imaging instruments used, with institution and field strength indicated. Although all the proton metabolites can be seen in the spectrum, note that because it was acquired in a whole-head, nonlocalized fashion, only the NAA peak is implicitly localized to the brain. The area of the NAA peak of the subject SS, was integrated in each subject as shown and converted into absolute millimoles, QNAA, by comparing with the NAA peak area, SR, in a reference phantom of known concentration as described by Eq. 1. Note the excellent signal-to-noise ratio of this short acquisition and the nearly total elimination of the skull’s lipid signals from obscuring the spectrum.
- Fig 2.
Box plot showing the 25%, 50% (median), and 75% quartiles (box) and ±95% (whiskers), of the distributions of the subjects’ WBNAA concentrations in each of the 4 institutions, 5 scanners, 3 field strengths, and 2 manufacturers used in this study. Note that the differences among the distributions (means and SDs) are statistically insignificant, independent of the (healthy) subjects’ age or sex, indicating that the methodology is robust to instrumentation differences.
Tables
Estimated mean ± SD NAA concentrations at each institution.
Institution Subjects Scanner Field, Manufacturer, Model Mean WBNAA (mmol/L) SD (Unadjusted) (mmol/L) SD (adjusted) First n = 23 1.5 T, Siemens, Vision 11.7 1.3 1.3 Second n = 31 1.5 T, Siemens, SP63 12.3 1.1 1.1 Third n = 24 1.5 T, Siemens, Vision 12.6 1.2 1.2 n = 12 3.0 T, Siemens, Trio 11.7 1.1 1.1 Fourth n = 11 4.0 T, GE, Signa 5.x 12.8 1.5 1.5 Total n = 101 12.2* 1.2* 1.2 Note:—WBNAA indicates whole-brain N-acetylaspartate. The SDs are presented as both unadjusted and adjusted with respect to confounding effects from age and gender (differences were in second decimal digit or smaller).
* Average of all subjects at all institutions.
